Floating structures in a body of water may be subject to wave and/or current induced motions such as heave, pitch, and/or roll. For passenger vessels, such as cruise ships, it is desirable to minimize these motions due to sea-sickness and the comfort of the passengers. For cargo vessels, it is desirable to minimize these motions to protect the cargo. For offshore drilling and/or production vessels it is desirable to minimize these motions due to safety of the crew and connections and fatigue of lines to the vessels, such as drilling pipes, import and export lines, tendons, umbilicals, and others.
For ships, active and passive motion suppression devices, such as gyroscopes, specially designed hulls, tanks, moveable weights, springs, and wings, have been used to suppress motion. Most such devices work when the ship is in motion. It is generally more difficult to suppress the motion of a stationary ship.
U.S. Pat. No. 6,910,438 discloses an oscillation suppression system to inhibit vertical and rotational resonance of a floating platform. The oscillation suppression system includes energy absorption chambers mounted in or about the hull of the floating platform. The chambers may be separately attached or integrated as part of the structure. The chambers are comprised of gas in an upper portion, and water mass in a lower portion. The chambers are closed or partially vented at the upper ends and open at their bottom ends. The enclosed gas in the upper portion of the chamber acts as a gas spring reacting against the floating platform and the water mass. The suppression of resonant oscillations of the floating platform system is accomplished through the gas-spring pressure changes acting on the floating platform system in phase opposition to external forces. U.S. Pat. No. 6,910,438 is herein incorporated by reference in its entirety.
There is a need in the art for improved systems and methods for suppressing motions of floating structures.
There is a need in the art for systems and methods for suppressing motions of floating structures that do not suffer from the disadvantages of the prior art.
There is a need in the art for systems and methods for suppressing motions of floating structures at different excitation frequencies.
There is a need in the art for systems and methods for suppressing motions of floating structures at multiple excitation frequencies.
These and other needs will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.